Process for producing olefins and aromatics by the catalytic cracking of a naphtha



3,284,341 ATALYTIC Nov. 8, 1966 A. M. HENKE ETAL PROCESS FOR PRODUCING OLEFINS AND AROMATICS BY THE C CRACKING OF A NAPHTHA 2 Sheets-Sheet 1 Filed March 20, 1964 m N w ATTORNEY NOV- 8, 1966 A. M. HENKE ETAI. 3,284,341

PROCESS FOR PRODUCING OLEFINS AND AROMATICS BY THE CATALYTIC CRACKING OF A. NAPHTHA Filed March 20, 1964 2 Sheets-Sheet 2 m W .,Nkww m e uw., m ,Ww wm mm mh Nw mw S. W a .a a n IW/ N M M ,M m OMGN N N f E fra Z w 5W QM M Y f RQ wf B auw WQ. QN/y Wl Smm United States Patent O Filed Mar. 20, 1964, Ser. No. 353,390 2 Claims. (Cl. 208-120) This invention relates to the manufacture of oletins and aromatic hydrocarbons, .particularly oleiins containing labout 2 to 5 carbon atoms and aromatic hydrocarbons containing about 6 to 8 carbon atoms.

The conversion of naphthas and/ or gasoline into olelins and aromatic hydrocarbons is a process of considerable economic interest, particularly when there is `an o-ver supply of gasoline. Such conversion is known in the prior art. However, this known process has sulered from certain weaknesses. One important deficiency is the relatively low rat-io of olefins and aromatics formed vs. gases and coke. Thus, these previously known processes give a relatively poor selectivity, form-ing relatively large amounts of low value materials such as gases and coke and relatively small amounts of the desired more valuable materials, namely oleiins and aromatics.

This invention has for its object to provide improved procedure for converting naphtha and/or gasoline into oleiins and aromatic hydrocarbons. Another object is to provide improved procedure for converting naphtha and/or gasoline into oleiins and yaromatics with high selectivity. Another object is to improve the state of the art.

These and other objects are accomplished by our invention which includes contacting a naphtha or gasoline with a silica yalumina cracking catalyst at a space velocity above about 4.5 at a pressure between labout and 20 p.s.i.g. and at a temperature between about 1000 and 1200 F., the temperature being such as to give `a conversion of :above abo-ut 40 percent at the spa-ce velocity and pressure employed. We have found in accordance with our invention that this method of operation -results in an unusually high selectivity in regard to formation of oleiins .and aromatics.

The feed stock employed in our process can be any hydrocarbon mixture which boils predominantly in the range between about 100 and 450 F. Thus, `the feed stock 'may be a straight run naphtha or gasoline, a naphth-a or lgasoline prepared by catalytic cracking c-r even a gasoline prepared by reforming in `the presence of hydrogen. It will be evident that the feed stock may be primarily naphthenic, primarily aliphatic, primari-ly aromatic or mixtures of any of these three types of hydrocarbons. We prefer to employ feed stocks which are' primarily aliphatic, primarily napthentic or mixtures of these two types of hydrocarbons. Since the process ordinarily does not result in complete conversion, we contemplate employing as part of the feed stock recycle unconverted hydrocarbons.

The space velocity employed in our process must be -above about 4.5 and -is preferably between `about 6 and 8 liquid volumes of feed stock per volume of catalyst per hour. It will be .apparent from data presented hereinafter that utilization of space velocities below about 4.5

3,284,3li Patented Nov. 8, 1966 results in much poorer selectivity. While space velocities above about 8 may be employed, we do not include such space velocities las being within the scope of our invention since they are less economical and as will appear from data presented below such higher space velocities do not result in a material improvement in selectivity.

In addition to space velocity, the pressure employed in our process is a vitally important matter. The pressure may be atmospheric pressure or O p.s.i.g. On the other hand, pressures up to about 20 p.s.i.g. may be employed in accordance with our invention. Also, slightly reduced pressures such as 600 t-o 760 mm. of mercury absolute may be employed. There does not appear to be any advantage in using slightly reduced or slightly elevated pressures and we 4prefer to operate our process at about atmospheric pressure.

The catalyst employed in our process must be an active catalytic cracking catalyst of the silicia alumina type. Any such silica alumina cracking catalyst Imay be ernployed. While we prefer to employ conventional silica alumina cracking catalystcontaining minor amounts of alumina such as about l0 to 25 percent, it is entirely satisfact-roy lto employ other types of silica alumina cracking catalysts such as those having larger `amounts of alumina which have been recently developed. Such recently developed catalysts contain between about 30 and 50 percent alumina. The catalyst may be a natural or .synthetic silica alumina cracking catalyst. Also, it may be used in the form of `a fixed bed or in a moving bed such as is customarily employed in conventional catalytic cracking processes. It should have an Activity Index of between about 25 and 35. When the Activity Index drops below this value, as a result of continued use in the process, the catalyst should be discarded and replaced with fresh catalyst.

The temperature employed in our process is maintained :at between about 1000 and l200 F. and Preferably at between about 1050 and ll F. The temperature does Inot have a large or pronounced effect on selectivity. However, it must be adjusted so that a suitable degree of conversion, i.e. -above Iabou-t 40 percent is -obtained and preferably between about 50 and 80 percent conversion.

The above-described process is carried out or continued until the catalyst requires regeneration. This is generally indicated by a drop in conversion to below the desired value of about 40 percent. Then the catalyst is regenerated in conventional fashion by combustion. After regeneration the catalyst is again reacted in the process. As will appear from the data presented hereinafter, we have found it advantageous to continue the onstream reaction for a throughput of between about 1 and 8 before regenerating the catalyst.

Regeneration results in reactivation of the catalyst. However, after repeated regeneration the catalyst becornes permanently deactivated and therefore should be replaced.

In the above discussion and in the following example and claims the terms conversion and selectivity are used. Conversion is defined as being equal to the sum of the following percentage yields (percent by weight of naphtha charged).

Total Percent C5 and Lighter-l-Total Percent Net Aromatics-l-Total Percent Coke.

Selectivity is defined as being equal to:

Total percent CfC Olens-l- Total percent Net Aromatics Total percent C5 and Lighter Gas-i-Total percent Net Aromatics-I-Total percent Coke Example grams per liter, respectively. The catalyst employed in l5 these experiments was a fixed-bed catalyst composed of a commercial silica alumina cracking catalyst (Ameri- 4 highest selectivity was obtained at 8 LHSV while the lowest was obtained at 0.5 LHSV. The results of these runs, as well as the reaction conditions employed, are given in Table II. It will be noted that Table II also shows the effect of different temperatures.

TABLE I.-KUWAIT NAPHTHA Gravity: API 59.9

Distillation (D86):

IBP: F

Sulfur-ppm.:

Total can Cyanamid Triple A). This catalyst had a mesh size 560 o Mercaptan 31 of 10-20. It was dried at 250 F. and calcined at o Hydrocarbon group type- 1000 F. prior to use 1n the experiments. In these ex- 20 FIA Pernt b v01 periments the preheated naphtha was introduced into the A y bottom of a stainless steel b h l v romanes 10'8 enc sca e reactor contain- Olens 0 7 ing a xed bed of the catalyst. Vapors of the naphtha Saturateg 88'5 feed flowed upwardly through the bed of catalyst and Mas ectrome'lfi'n'e"tgnwere removed from the upper end of the reactor. The SPSP m creen Yvo 6 reaction products were cooled and analyzed as indicated can; ns hereinafter. yc Opara ns In certain of these experiments the effect of space ve- Blcycloparafns 0'9 locity was determined by employing various space ve- Alkylbenzenes 128 iociiies between about 0.5 LHSV and 8.0 LHSV with ail Benzene 01 other conditions nearly constant. These runs were made Toluene 1-2 in l-hour cycles. The resulting conversions ranged C8 4.0 from 31 to 73 percent by weight of the charge and the C9 5.2 resulting selectivities ranged from 46 to 76 percent. The C10 2 3 TABLE II Process Conditions:

Temperature, F 1, 004 1 023 l, 050 999 1, 023 1, 051 1, 072

Pressure, p.s.1.g 0 0 0 0 0 0 0 Space Velocity, V01./Hr./V01 0. 5 0 5 0 5 1. 0 1 0 1 0 1. 0

Throughput Interval, From Vo1./V 01. to Vo1./V o1 0-2 0-2 0-2 0-2 0-2 O-2 0-2 Product Yields, Percent by Wt. of Charge:

Gas (C5 and Lighter) 34. 9 40. 7 43. 5 28.8 33.1 40. 9 43. 8

Paramus and Hydrogen 20.5 2s. 4 24. 7 ie. 7 16.0 20. 5 2o. 4

Hydmgpn 0. 6 0. 9 1. o 0. 4 o. 5 0. 9 1. Methane 2. 7 3. 6 4.3 2. 0 2. 0 2. 9 3.41) Ethane 1. 4 1. 8 2. 4 1.0 1.0 1. 5 2. 2 Propane 4. 2 5. 0 5. 3 3. 7 3. 0 3. 9 3. 9 iso-Butane 5. 7 5. 9 5. 6 5. 1 4. 8 5. 5 4. 4 ii-Butane 1.5 1.7 1.9 1.1 1.1 1.5 1.5 iso-Pentane 3. 9 4. 0 3. 4 3. 0 3. 2 3. 8 2. 8 n-Peritanc 0. 5 0. 5 0. 8 O. 4 0. 4 0. 5 0. 6

oiens. 14. 4 17. 3 18. 8 12. 1 17. 1 20. 5 23. 4 Ethylene 1. 6 2. o 2. 3 1, 6 1. 8 2. 3 2. 9 Propyipnp 5. 7 7.1 s. o 5.1 7. 4 9.0 9.9 Bilfenos 4. 7 5. 7 6. 1 3. 4 5. 5 6. 8 7. 6 Penipnes 2. 4 2. 5 2. 4 2. 0 2. 4 2. 4 3.0

Liquid (Ca and Heavier). 61. 3 54. 7 50. 9 68. 9 64.

Aromatics, Total. i9. 9 19. 4 2o. o i6. 7 2o. i i Aromatics, Net--- 7. 1 6. 6 7. 2 3. 9 7. 3 s. 3 9. 8

ook@ 3.8 4.6 5.6 2.3 2.2 3.5 4.5 Liquid Product:

C and Heavier, Percent by Vol. of Charge 67.0 60.7 56. 2 74. 0 9.

Alomatics, Percent by Voi. of Charge 16.8 16. 4 16.9 14. 1 i7. ii- Conversion, Percent 45.8 51. 9 56. 3 35. 0 42.6 52. 7 58. 1 seieetivity, Percent 46. 9 46. 1 46. 2 45. 7 57. 3 54. 6 57. 1 Liqid PriduoctArIoperties:

ravi y, 57.1 56.1 54.9 6

FIA, Percent by Volume: 0 0 58 8 57 1 55 6 nrnstics 25.58) 31.? 18. 8 23. 6 29. 1 34. 1

ein 3. 3.4 5.1 3.3 3.8

Saturates-- 71.8 68.3 6 .1

Distmaton D 8 5 77 8 71 3 67.6 62.1 Overpoint, F 100 90 92 89 End point, F 508 432 488 49o TAB LE lL-Contnued moon/ 5 0 45706035 5 1176 4571 4639 7. 749 1 4m. 9 7. 921.94L90. 2. 3.0.62 9 .5L 5.5.60. 9 %.4L 1., 3 1 2 1 5 6146 5 7 M002 7 0 58925876 7 9134 4249 2208 l 668 0 4 5 9 3. 0.L0.23.0.2.0. 6 .L /.5.2 996i 3.6.90 9 4.4.0. 1M. 2 1 I 61 7136 5 2 7 @002 7 0 132671007 7 5570 34000 02902 8 550 n 1 3.5 9 L L5.B... 3.L2.0 & 4293. 6.07.4. 1.7.1.9 3. 5.40 1| 4 2 2 1 42 5165 5 3 6 9002 8 8 87463046 0 8020 9683 3699 D 037 mw 30 9. a 0.2L24.L3.0. a 2.0.7.3. 7.96.2 4.690. 9 6.5. 1J 3 1 2 1 51 614.6 5 2 mouw 6 2 468140074 4 7403 6688 4722 5 532 0 3. 7. 2. 0L02 .020. L .2 0. .5.L 555.0. 9 25 1J 2 1 n u 6.0 7m 7136 5 2 1 2 7. 5. L .L .0. .5. 0.9 .7. 5. 15123 0 2 3. .L 1 12 0 20 a.. 0. .0 95.90 9 261. 14123 m N IOA v E O l m e Q 10 g om .N .ma 1. h .h 0 C .m0 V .m Vf .l 0 0m D V. N0 t e .D11 W g 0 0 LV e v. r t n m .m e ey S l1 b) V. V N C10 E u .a br I .l dv nH m et r o z F Vu eh d n e. e H Pm m V GFF um um n e e n m um.. u ...cmLoLy 0 5 F ...1.51 mL a www@ .m .lm m .m a pw. 55mm. www5 Mmmm @mmm m ....Pmmn .m.m%%% .1t MP du v etr0 0 q true 0 r ces. ecu a=a0DD000 .mmwww mw m HMEPnmn m EPBP A wHmpnPmmumm mmmd159 1 a. 1 Pt @mman Y@ a l m mdamYmP r1 auvn mSMO .ES P 0 u w PmmdmP MAAOSOE Ser. 0 5 .1dr .l H epm ma M d l S cTPST dG L C .mCAvcuGF D 0 0 Q UGG. r. r .1 Odi P P L CSL It will be noted from the data presented in Table II that the space velocity has a pronounced effect ori selectivity at any given temperature and conversion level. The results of the data presented in Table II are presented in graphical form in FIGURE 1 of the accompanying drawing. Referring to this drawing in which space velocity is shown on the abscissa of the graph and selectivity is shown ori the ordinate of the graph, it will be noted that operation between about 4 and 8 space velocity has a very beneficial effect on selectivity. The

temperature, however, does not alTect selectivity although conversion increases as the temperature increases.

Several runs were also conducted in order to show the beneficial eiect of employing a pressure of about atmospheric pressure. Thus, in these runs various pressures between and 200 p.s.i.g. were employed at otherwise constant conditions of 1050 F., 2.0 LHSV utilizing l-hour cycles. The results of these various pressure runs are given in Table III and are graphically presented in FIGURE 2. In FIGURE 2 percent conversion is plotted puts is not necessary and our invention is not restricted thereto.

What we claim is:

1. A highly selective process for the catalytic conversion of a hydrocarbon feed stock selected from a naphtha-gasoline fraction boiling in the range of between about 100 and 450 F. which comprises contacting said feed stock with a silica alumina cracking catalyst containing about 10 to 50% alumina at a liquid hourly space velocity between about 4.5 and 8, at a pressure between about 600 mm. and p.s.i.g., and at a temperature between about l000 and 1200 F., thereby producing a high yield of mixed olefinic hydrocarbons having from 2 to 5 carbon atoms and mixed aromatic hydrocarbons having from 6 to 8 carbon atoms and a reduced yield of saturated gaseous hydrocarbons and coke.

2. The process of claim 1 wherein the silica alumina cracking catalyst contains about 10 to 25% alumina, and

against percent selectivity. 20 the process is carried out at a space velocity of between TABLE III Process Conditions:

Temperature, F 1, 050 1, 045 1, 048 1, 054 1, 054 1, 048 0 1 20 50 100 200 2.0 2.0 2.0 2.0 2.0 2.0

Product Yields, Percent by Wt. of Charge:

Gas (Cs and Lighter) 33. 1 36. 4 39. 9 44. 8 47. 5 54. 4

Paratins and Hydrogen 14. 0 18. 7 24. 4 32. 6 40. 3 50. 7

Hydrogen 0. 5 0. 5 0. 7 0. 5 0. 5 0.4 Methane.. 1. 8 2. 6 3. 8 5. 5 7. 2 9. 4 Ethane- 0.9 1. 4 2. 4 4. 4 5. 3 7. 8 Propane. 2. 2 4. 0 5. 6 8. 8 11. 7 14. 9 iso-Butane 3. 8 5. 1 5. 7 6. 3 8.0 8. 6 n-Butane 0. 9 1. 4 2. 1 3. 0 3. 2 4. 7 iso-Pentane-. 3. 4 3. 2 3.4 3. 2 3. 5 4. 3 nPentane 0. 5 0. 5 0. 7 0. 9 0. 9 0. 6

Oleins 19. 1 17. 7 15. 5 12. 2 7. 2 3. 7

Ethylene 1. 9 1. 9 2. 1 1. 7 1. 1 0. 8 Propylene. 7. 7 7. 3 6. 6 4. 5 2. 7 1. 0 Butenes 6. 5 5. 7 4. 2 4.1 2. 4 1. 3 Pentenes 3. 0 2. 8 2. 6 1. 9 1. 0 0. 6

Liquid (Cs and Heavier). 64. 8 61. 0 55. 6 48. 9 44. 8 34. 4 Aromatics, Total. 18. 5 19. 3 19. 8 18. 1 17. 4 16.1 Aromatics, Net 5. 7 6. 5 7. 0 5. 3 4. 6 3. 3 Cn'L-n 2. 1 2. 6 4. 5 6.3 7. 7 11.2

Liquid Product:

Cs and Heavier, Percent by Vol. o!

Charge 70. 7 66. 5 60. 5 54.0 49. 0 38. 5 Aromatics, Percent by Vo of Charge 15. 6 16. 3 16. 7 15. 3 14.7 13. 6 Conversion, Percent.- 40. 9 45. 5 51. 4 56. 4 59.8 68. 9 selectivity, Percent 60.6 53. 2 43. 8 31. 0 19. 7 1U. 2 Liquid Product Properties:

Gravity, API 59. 6 57. 8 56. 9 54. 8 54. 6 49. 7 FIA, Percent by Volume:

Aromatics 22. 0 24. 4 28. 1 29. 8 30. 9 39. 5 Olefinsm. 6. 1 4. 2 3. 9 3.0 1. 9 1.1 Saturates 71. 9 71. 4 68. 0 67. 2 67. 2 59. 4 Distllation, D-86:

Overpoint, F 104 88 1 End point, 417 466 525 F 170 166 181 256 250 264 330 331 460 From the results presented in Table III and in FIG- URE 2 of the drawing it will be evident that it is vitally necessary to employ relatively moderate pressures such as 0 to 20 p.s.i.g. if relatively high selectivities such as above about 40 percent are to be obtained.

We have also found that throughput has some effect on selectivity. Thus, the selectivity improves with the length of the on-stream cycle. However, we prefer not to operate beyond a throughput of' about 8 between regenerations. While this improvement in selectivity with increasing throughput is relatively minor as compared with the eiect of space velocity and pressures, nevertheless we prefer to employ a throughput in the range mentioned and the use of such a throughput is included within the scope of our invention. However, it is to be understood that the use of such moderate throughabout 6 and 8, a pressure between about 0 and 20 p.s.i.g., and a temperature between about 1050 and 1170 F.

References Cited by the Examiner UNITED STATES PATENTS 9/1945 Bailey 260-683 DELBERT E. GANTZ, Primary Examiner.

A. RIMENS, Assistant Examiner. 

1. A HIGHLY SELECTIVE PRICESS FOR THE CATALYTIC CONVERSION OF A HYDROCARBON FEED STOCK SELECTED FROM AN NAPHTHA-GASOLINE FRACTION BOILING IN THE RANGE OF BETWEEN ABOUT 1000 AND 450*F. WHICH COMPRISES CONTACTING SAID FEED STOCK WITH A SILICA ALUMINA CRACKING CATALYST CONTAINING ABOUT 10 TO 50%% ALUMINA AT A LIQUID HOURLY SPACE VELOCITY BETWEEN ABOUT 4.5 AND 8, AT PRESSURE BETWEEN ABOUT 600 MM. AND 20 P.S.I.G., AND AT TEMPERATURE BETWEEN ABOUT 1000* AND 1200*F., THEREBY PRODUCING A HIGH YIELD OF MIXED OLEFINIC HYDROCARBONS HAVING FROM 2 TO 5 CARBON ATOMS AND MIXED AROMATIC HYDROCARBONS HAVING FROM 6 TO 8 CARBONS AND A REDUCED YIELD OF SATURATED GASEOUS HYDROCARBONS AND COKE. 